The prosecution has called for murderer James Warnock to be given a whole-life term for the historic murder of Hampstead teenager Yiannoulla Yianni,

Warnock, 56, will be sentenced at the Old Bailey on Monday after he was today found guilty of raping and strangling the 17-year-old - having escaped justice for the brutal killing for more than half his lifetime.

The jury took just over two hours to return their verdict following the four-week trial which heard harrowing evidence of how the teenager was killed by sexual predator Warnock in the summer of 1982.

After the guilty verdict, Warnock pleaded guilty to six separate offences of possessing and distributing child pornography, details of which could not be reported during the murder trial.

Warnock had pleaded not guilty to murder, telling the court that he had enjoyed a summer fling with the teenager - but the jury did not believe his story, and the judge said today: “I am entirely satisfied that (Yiannoulla) had no previous sexual experience whatsoever.”

The defence called for a whole-life term to be considered because of the horrific nature of the crime, which the prosecution said amounted to “the subjection of physical and mental torture.”

The court heard how Yiannoulla - known as Lucy to her family - was chased around her home by Warnock in Belsize Road, before she was raped and strangled on her parents’ bed, with a knife probably used to cut open her clothes.

Warnock had turned on the taps and filled the bath at some stage during the attack - which the prosecution argued would have added to the teenager’s anguish, if she was conscious.

Prosecuting barrister Crispin Aylett said the tissue of lies woven by Warnock and his attempt to defame Yiannoulla’s character amounted to “a complete lack of remorse.”

The court heard victim impact statements from Yiannoulla’s brothers and sister, where they spoke movingly of the shattering effect the murder has had on their lives.

Her brother, Rick, suffered from depression and recurrent nightmares for years, and said that being put through the trial after Warnock pleaded not guilty had forced the family to relive their worst moments.

He sought counselling in the build -up to the court case and is on medication, and said the trial has had an adverse effect on his elderly mother’s health.

His father died of a brain tumour five years after Yiannoulla’s death, and he said: “I truly believe this was as a direct result of Lucy’s murder.”

He added that he was grateful to the police for their work in finally bringing Warnock to justice, and said: “I have no doubt that he will pass through the gates of hell”.

Another brother, Peter, was on holiday with his sister Maria in Cyprus - where the family is originally from - when Lucy was murdered.

He said his parents were so devastated that he felt unsupported, and that his environment from that moment on was “saturated with grief.”

He said: “I became the boy whose sister was murdered...My adolescent life was non-existent.”

He added that as an adult, although he has built a family life with two sons, he constantly worries about their safety and has struggled to form close relationships.

He added: “This man took my sister’s life in the most terrible and violent way - then tried to dishonour her memory. Luckily, we defended (her) honour.”

His sister, Maria, spoke of how close she had been to Yiannoulla, who was awaiting ‘O’ level results from Quentin Kyanston School and hoped to become a beauty therapist when her life was cut tragically short.

Maria has called one of her own daughters Lucy, in her sister’s memory, but said that her children’s lives have been plagued by her “fears and irrational behaviours”.

She added: “The defendant has had 34 years to live his life, while ours has been nothing but torture,” saying that she has known only fleeting moments of happiness since losing her sister.

Following the guilty verdict, Warnock’s defence barrister argued that the murder was “a spur of the moment offence” after the tiler went to the Yianni home to try and seduce the teenager, but was spurned.

George Carter Stephenson said: “He was chancing his arm, perhaps believing that he could win over Yiannoulla.”

The defence also asked that Mr Warnock’s age of 22 at the time of the of the murder be taken into consideration.

Mr Carter Stephenson added that Warnock had not been in trouble with the police for “ a substantial number of years” until his arrest for child pornography offences - which led to his DNA being taken and his subsequent conviction for the long-unsolved murder.

The judge said he would have to consider whether there had been “a significant degree of planning” prior to the murder in considering the length of his sentence.

Under current law, such a murder would be automatically eligible for a whole-life tariff - but the judge must take into account the law as it was in 1982 when he passes sentence.

Warnock will be sentenced concurrently for the six offences of possessing and distributing indecent images of children on Monday morning.